CLE TRACON CTLR EXPERIENCED OPERROR AT APPROX 3000 FT WHEN ASSUMING CONFLICTING TFC WOULD BE DSNDING.

Narrative

THE EMBRAER 145 WAS ON A WESTERLY HDG; INBOUND TO CLE RWY 24R. THE ITINERANT ACFT WAS NEBOUND; ARRIVING BURKE LAKEFRONT (BKL) ARPT. I HAD ASSUMED THE RADAR POS ABOUT 3 MINS PRIOR TO THE SIT. I INITIATED A DSCNT ON THE E145 TO 3000 FT. I ERRONEOUSLY ASSUMED THE BKL ARR WOULD BE DSNDING; AS THEY WERE LESS THAN 5 MI FROM THEIR DEST. THE E145 CONTINUED WBOUND ACROSS THE FINAL APCH COURSE. I INSTRUCTED THE E145 TO MAINTAIN PRESENT ALT AND POINTED OUT THE TFC. I ALSO TURNED HIM L. THE EMBRAER PLT SAID HE HAD THE TFC IN SIGHT PREVIOUSLY; BUT HAD LOST SIGHT OF IT. (HAVING THE TFC IN SIGHT WOULD HAVE BEEN PRIOR TO THE ACFT GETTING CLOSER THAN 3 NM.) AFTER THE 2 ACFT PASSED; THEY CONTINUED ON VISUAL APCHS TO THEIR DESTS. I BELIEVE THAT MY ASSUMPTIONS CONTRIBUTED TO THE PROB. I WAS TOLD THE ITINERANT ACFT WAS DSNDING INTO BKL; SO I THOUGHT HE'D PROBABLY BE BELOW THE E145. I KNEW THE ITINERANT WAS N OF THE RWY 24R FINAL APCH COURSE THAT THE E145 WAS INBOUND FOR. I ASSUMED THE E145 WAS GOING TO JOIN THIS FINAL OR PROCEED TOWARD THE ARPT. AS STATED EARLIER; THE E145 DID NOT JOIN THIS COURSE.